Fall In PaO2 Research Articles

Hypoxaemia created by pulmonary oedema after pulmonary microemboli in dogs.

Pulmonary microemboli may play a role in the adult respiratory distress syndrome, creating both pulmonary oedema and hypoxaemia. We measured the time course of pulmonary oedema and hypoxaemia after pulmonary microemboli of 63-74 mu starch were infused into dogs. Dogs were divided into two groups: six dogs that did not develop pulmonary oedema, and seven that did. Immediately after emboli there was no difference between groups in the large fall in PaO2 or the rise in Qs/Qt. Therefore the hypoxaemia of pulmonary embolism is not created by pulmonary oedema. As pulmonary oedema increased with time in the oedematous dogs, PaO2 fell further. There was no further reduction in PaO2 in the dogs who did not develop pulmonary oedema. We conclude that hypoxaemia after pulmonary embolism may be worsened if pulmonary oedema occurs, but the immediate large reduction in PaO2 after embolism is not created by pulmonary oedema.

Nocturnal hypoxaemia in chronic obstructive pulmonary disease.

1. Day and night arterial oxygen saturation (Sao2) has been measured in forty-one patients with chronic obstructive pulmonary disease (COPD), mean FEV1 0.84 (range 0.4-1.4)litres, and with a range of daytime Sao2 values of 67-95%. 2. The mean and biggest falls in Sao2 at night were much greater in the patients with lower daytime saturations. However, when falls in arterial oxygen tension (Pao2) were estimated from the decreases in Sao2, there was no correlation between the estimated biggest fall in Pao2 and daytime Sao2 and only a weak correlation between estimated mean fall in Pao2 and daytime Sao2. 3. Measurement of ventilation in four hypoxaemic patients with COPD (range 60-90% Sao2) by respiratory inductance plethysmography showed that nocturnal hypoxaemic dips were accompanied by diminished ventilation, which was not always shown by nasal thermistors. 4. Because nocturnal hypoxaemic dips are transient the ideal alveolar-arterial oxygen difference, which assumes a constant respiratory exchange ratio, cannot be used to assess the mechanism of hypoxaemia. 5. Erythrocyte mass was strongly correlated with daytime Sao2 but this correlation was not significantly improved by including nocturnal hypoxaemia in the regression. 6. The results suggest that greater falls in Sao2 at night are related to lower initial Sao2 values and that the cause may be a reduction in ventilation.

Spinal Anesthesia or General Anesthesia for Emergency Hip Surgery in Elderly Patients

One hundred and thirty-two elderly patients undergoing emergency hip surgery were randomly allocated to receive subarachnoid block (SAB) or general anaesthesia (GA). Using the 125.I fibrinogen uptake test, deep vein thrombosis was found to occur in 17 of 37 patients in the SAB group and 30 of 39 patients in the GA group (P 0.05). Blood loss was 513 ml (+/- SEM 44) in the SAB group and 714 ml (+/- SEM 67) in the GA group (P less than 0.01). Hypoxaemia was present preoperatively (mean PaO2 9.2 kPa). Immediately following general anaesthesia, the mean fall in PaO2 was 0.86 kPa compared with preoperative values but only 0.16 kPa following subarachnoid block (P less than 0.01). At 24 hours postoperatively the fall in PaO2 was similar in both groups and recovered only slowly during the first week. Twelve patients died, three in the SAB group and nine in the GA group. This difference in mortality was not statistically significant.

Changes in arterial oxygenation and pulmonary shunt during thoracotomy with endobronchial anesthesia

Eight-five veterans underwent thoracic operations, mainly for carcinoma of the lung, with the aid of endobronchial anesthesia. Changes in arterial oxygenation (PaO2) and pulmonary shunt (Qs/Qt) were determined sequentially. Mean PaO2 after both lungs were ventilated for 20 minutes, supine, with 100% oxygen was 433 +/- 8 mm Hg. Selective ventilation of one bronchus dropped this value significantly (p less than 0.01) to 247 +/- 13 mm Hg. PaO2 did not change appreciably when the patient was turned to the lateral position; however, following pleurotomy there was a significant (p less than 0.01) decline in mean PaO2 to a nadir of 178 +/- 17 mm Hg at 90 minutes. Transient hypoxemia (PaO2 less than 60 mm Hg) occurred in 11 of 85 patients, most frequently (7/11) during positioning. Preoperative PaO2 PaCO2, forced expiratory volume in 1 second, forced vital capacity, or medical status did not predict hypoxemia. Qs/Qt increased significantly (p less than 0.01) at the onset of atelectasis from 18% +/- 0.9% to 25.4% +/- 0.9% but did not change with turning. The maximal mean Qs/Qt (30.3% +/- 1.1%) occurred immediately after opening the pleura and then decreased significantly (p less than 0.05), despite the fall in PaO2. Blood loss greater than 1,000 cc (n = 10), especially with hypotension, resulted in a significant increase (p less than 0.05) in Qs/Qt and a fall in PaO2. Thus pulmonary vascular adaptation to acute atelectasis has been demonstrated in man, and this, as in animal models, fails with hemorrhage.

Single versus multiple pulmonary emboli: different haemodynamic and blood gas results.

We evaluated haemodynamic and blood gas changes following the intravenous infusion of starch microemboli (63-74 mu). Comparisons were made between dogs receiving a single embolus and dogs receiving an equal quantity of embolus divided into small doses given at 30 minute intervals (multiple emboli). The most significant finding was that the same quantity of embolus produces different effects. In the dogs receiving a single embolus of 150 mg kg-1 of starch. Pao2 fell from 11.3 to 7.6 kPa (85 to 57 torr)(p less than 0.025) and Qs/Qt increased from 11 to 34 per cent (p less than 0.01). In the multiple emboli dogs, after a total dose of 150 mg kg-1 of starch, there was a small but not significant fall in Pao2 from 11.6 to 10.8 kPa (87 to 81 torr), and Qs/Qt did not change significantly. In the single embolus dogs Q increased significantly after an embolus of 100 mg kg-1 of starch (p less than 0.05). after a single embolus of 150 mg kg-1, Q was variable; 3 dogs showed a decrease, and 2 an increase, however the mean change was not significant. In the multiple emboli dogs, Q decreased significantly (p less than 0.005).

Hypoxemia and pulmonary gas exchange during hemodialysis.

With measured values of arterial blood gas tensions, of expired respiratory gas fractions, and volume of the expired ventilation, the determinants of alveolar oxygen tension (PAO2) were used to evaluate their influence on the development of the arterial hypoxemia that occurs in spontaneously breathing patients undergoing hemodialysis using an acetate dialysate. Dialysis produced no significant changes in the alveolar-arterial O2 tension gradient (AaDO2). The extracorporeal dialyzer removed an average of 30 ml.m-2.min-1 of CO2. Accordingly the pulmonary gas exchange ratio (R) dropped from a mean predialysis value of 0.81 to 0.62 (P less than 0.001). The arterial CO2 tension remained constant throughout, whereas the minute ventilation, both total (P less than 0.01) and alveolar (P less than 0.01), decreased during dialysis. This decrease in ventilation accounts for more than 80% of the fall in PAO2. During dialysis there was a decrease (P less than 0.001) in arterial oxygen tension (PaO2), which varied among the individuals from 9 to 23% of control. During the postdialysis hour PaO2 returns to control values concomitant with increase in ventilation. The quantitative gas exchange relationships among R, alveolar ventilation, and AaDO2 predict the PaO2 values actually measured.

Chest Physical Therapy: The Immediate Effect on Oxygenation in Acutely III Patients

There is no documentation in the literature of the risk of hypoxemia after chest percussion in acutely ill adults with nonsurgical pulmonary disorders. We studied the immediate effect of postural drainage and chest percussion (PDP) on oxygenation in 22 hospitalized patients with a variety of acute, nonsurgical pulmonary disorders. Heart rate, respiratory rate, blood pressure, and arterial blood gas levels were measured at four points before, during, and after PDP. There was a significant fall in PaO2 after chest percussion in ten patients who produced no sputum or small amounts of mucoid sputum. The mean PaO2 fell 16.8 mm Hg (P < 0.05) immediately after PDP, when compared to the value obtained after postural drainage alone, and had fallen another 5.3 mm Hg (P < 0.01) 30 minutes after return to the pretreatment position. There was no significant change in PaO2 in 12 patients who produced moderate to large amounts of mucopurulent secretions. The fall in PaO2 was probably due to increased ventilation-perfusion mismatch since this fall was avoided in two patients restudied while receiving 100 percent oxygen. We concluded that all acutely ill patients receiving PDP should be carefully monitored and, if necessary, should receive increased levels of inspired oxygen to avoid hypoxemia. Our data suggest that the use of PDP in patients without sputum production is not indicated and is potentially dangerous.

Mechanisms Responsible for the Sustained Fall in Arterial Oxygen Tension after Endotracheal Suctioning in Dogs

Because a sustained fall in arterial oxygen tension (PaO2) was observed after endotracheal suctioning in previous studies on anesthetized dogs and in humans, this study was designed to investigate the nature of the fall, its duration, and its response to several challenges. Experiments were performed at weekly intervals using three anesthetized dogs. Each dog was subjected to five experiments. In spontaneously breathing dogs, the duration of the sustained fall after suctioning or after suction catheter insertion without application of suction pressure persisted through 15 minutes. At 30 minutes afterwards, PaO2 had partially or completely returned to control levels. One hyperinflation breath given after suctioning did not produce a lasting reversal of the sustained fall, and pretreatment with isoproterenol mist inhalations failed to prevent the sustained fall. In dogs which were mechanically ventilated both before and after suctioning or catheter insertion without application of suction pressure, three hyperinflations before suctioning or pretreatment with isoproterenol failed to prevent the sustained fall. The data supported the hypothesis that a reflex mechanism, initiated by mechanical stimulation of the airways, was responsible for the sustained fall in PaO2 observed.

Association of hemorrhagic disease and the syndrome of persistent fetal circulation with the fetal hydantoin syndrome

indicate that death was due to massive intravascular sickling of red blood cells introduced during the procedure. The only other report of an occurrence similar to this involved a newborn infant who died seven days following an exchange transfusion in which donor blood with sickle cell trait was used? Intravascular sickling with resulting death can occur from the injection of the quantity of blood used in exchange transfusions if that blood contains cells with the potential for sickling. This reaction is likely if there is hypoxemia during or after the exchange transfusion. The need for both of these factors to be present (or others such as acidosis or dehydration) probably accounts for the paucity of reports such as this. In our patient, early findings indicated pulmonary hypertension with much right-to-left shunting ~ (persistent fetal circulation). The infant had repeated episodes of enhanced right-to-left shunting as suggested by periods of diminished Pa% without changes in Pae% or pH. Although he seemed to be improving, such an episode might have occurred after the exchange transfusion. The use of CPAP can result in a rapid fall of Pao2 if it is applied through nasal prongs; that System has been shown to have intrinsic problems which can lead to hypoxemia? -6 In any event, it is likely that our patient experienced an episode of hypoxemia which caused the intravascular sickling and death.

Bronchoalveolar lavage for the preparation of free lung cells: technique and complications.

Bronchoalveolar lavage at fibreoptic bronchoscopy enables the peripheral bronchoalveolar free cell population, which consists mainly of lymphocytes and macrophages, to be sampled. The yield is sufficient for detailed morphological and functional investigation of these cells, which can be separated by exploiting the glass-adherent or phagocytic properties of macrophages. Such studies are of particular interest in patients with recurrent chest infections, to detect abnormalities of local cellular immunity; in pulmonary fibrosis to assess activity of the disease and effect of treatment by observing morphology and testing function of free lung cells; and in bronchial carcinoma to investigate local immune responses to the tumour. The procedure is held to be ethical in these circumstances. The lavage consists of irrigation of a segmental bronchus through the fibreoptic bronchoscope with up to 500 ml pH-corrected normal saline solution. It is contraindicated in those with respiratory or cardiac risk, but is tolerated well by most patients. Complications include acute respiratory distress, vasovagal syncope and fever with pulmonary infiltrates. Lavage is associated with a mean fall of PaO2 of 3.0 kPa (22.7 mmHg) and routine oxygen supplementation is recommended.

Arterial oxygen tension changes in elderly patients undergoing upper gastrointestinal endoscopy. I. Possible causes.

Measurement of arterial oxygen tensions in elderly patients undergoing upper gastrointestinal endoscopy and in a matched control group undergoing colonoscopy showed a slight but significant fall in the PaO2 in both groups following premedication. The initial fall in PaO2 was probably due to the intravenous atropine, diazepam, and meperidine, mainly the latter. This fall of the oxygen tension continued in the gastroscopy group until the instrument was removed, while the controls rapidly returned to basal levels. This persistently reduced PaO2 in the former group is therefore most likely due to the physical presence of the endoscope in the pharynx. To minimize the occurrence of hypoxemia during gastroscopy, narcotics should probably not be used in the premedication of elderly patients. The procedure should be carried out after optimal oxygenation of the patient and be of short duration, and a narrow instrument may be useful in this group.

Abolition of a viscerosomatic reflex during oxygen deprivation.

Effect of hypoxia was studied on the J reflex, a term used for the reflex inhibition of muscular exercise by activation of type J pulmonary endings. Hypoxia was induced by ventilating the animal with gas mixtures varying from 18 to 9% oxygen in nitrogen. The blood gas tensions of the arterial blood (PaO2) were measured before, during, and after hypoxia. It was found that the J reflex is sensitive to a reduction in oxygen. A fall in PaO2 between 67 and 47 Torr abolished this reflex. Studies were also undertaken to exclude the possibility that the effect of hypoxia was predominantly exerted on monosynaptic reflex itself. A similar fall in PaO2 also depressed the monosynaptic reflex. Minimum time required for the significant depression was 32 s. On the contrary the J reflex was abolished within this period suggesting that the abolition of J reflex is independent of the changes in monosynaptic reflex during hypoxia.

Hypoxaemia in chronic obstructive bronchitis.

Arterial blood gas tensions were studied for six years in 85 patients (59 men, 26 women, mean age 58.8 years) with hypoxaemia associated with chronic bronchitis. All patients who died had a precipitous fall of arterial oxygen tension (PaO2) breathing air. In patients dying within two years of the first appearance of ankle oedema the mean rate of fall of PaO2 was 0.11 kPa/month. Patients who survived two years appeared to deteriorate more slowly (0.017 kPa/month) until some months before death, when they too deteriorated rapidly. Hypoxaemic patients with obstructive airways disease suffer a terminal rapid decline in arterial oxygen tension, which probably indicates real pathological change in the lungs and has important implications for long-term domiciliary oxygen treatment.

Arterial oxygen tension during active and quiet sleep in the normal neonate

The effect of sleep state on arterial oxygen tension was determined in ten healthy term infants by means of continuous transcutaneous PO2 monitoring. In all ten infants, PaO2 was significantly lower and more variable during active as compared to quiet sleep. This fall in PaO2 during active sleep was accompanied by asynchronous (or paradoxical) chest wall movement. These findings may be important in our understanding of the higher incidence of apnea during active sleep in both preterm and term infants.

Adverse effects of routine procedures on preterm infants.

Continuous monitoring of arterial oxygen tension (PaO2) in sick neonates has shown that handling the baby for reason often causes a fall in PaO2. Although the baby usually recovers spontaneously, a series of procedures one following closely upon the other may cause a prolonged fall in PaO2 necessitating respiratory support. This survey showed that infants were being disturbed at hourly or more frequent intervals, often for routine purposes, some of which do not justify the resulting hypoxia. Even simple procedures which are part of neonatal intensive care are hazardous and their routine use should be reconsidered.

PULMONARY COMPLICATIONS, VENTILATION AND BLOOD GASES AFTER UPPER ABDOMINAL SURGERY

Forty patients who underwent elective cholecystectomy were examined preoperatively and during the first postoperative week by physical examination, measurement of FVC and FEV1, arterial pH and blood gas analyses, and chest x-ray. Postoperative pulmonary complications (p.p.c.) were detected in 30 (75%) of the patients. Simple auscultation was the most sensitive tool in discovering p.p.c., but 18 of the 30 patients with complications also had a pathological chest x-ray. Obesity, smoking, postoperative naso-gastric tube and postoperative wound infection were predisposing factors for p.p.c. Six patients with preoperative pulmonary disease all had a progress in their lung pathology. There was no definite relationship of duration of anaesthesia or drainage of the abdominal wound to development of p.p.c. The patients with p.p.c. showed a deeper and more prolonged fall in Pao2 postoperatively than the normal group. None of the normals showed an arterial Po2 below 70 mmHg in the postoperative course, while 63% of the p.p.c. group did. FVC and FEV1 showed marked reductions from preoperative values on the first postoperative day, and then gradually increased to near preoperative values after 1 week. Arterial pH and Pco2, showed no definite changes during the postoperative course.

Arterial oxygenation during hemodialysis.

A FALL in partial pressure of arterial oxygen, or oxygen tension (Pao2), occurring during hemodialysis is a well described phenomenon.1 , 2 The published data, however, are disparate over its cause and clinical implications. Bischel, Scoles and Mohler3 described a small but statistically significant fall in Pao2 at the end of dialysis and concluded that pulmonary arterial microembolization from the dialysis membrane was its cause. Other authors1 , 2 , 4 have described a decline in Pao2 of greater magnitude during the course of dialysis. Craddock and his associates4 believed that the underlying mechanism was related to complement-mediated leukostasis in pulmonary capillaries. . . .

Studies in acid-base balance. I. Effect of alkali therapy in newborn dogs with mechanically fixed ventilation

The effect of rapid or slow infusion of hypertonic sodium bicarbonate on acid-base balance and serum osmolality was studied in 36 acidotic newborn dogs. Respiratory acidosis and hypoxia were produced by mechanically fixed hypoventilation. One group of animals breathed 100% O2 to prevent hypoxemia. Rapid infusion of HCO3- in acidotic and hypoxic animals resulted in only a transient (1 minute) and small (0.05 pH units) elevation of arterial pH followed by a continuous fall, resulting in a lower pH and a worsened metabolic condition than in the nontreated controls. In nonhypoxic acidotic animals, rapid infusion of HCO3- had little effect on arterial pH. PaCO2 increased suddenly by 17 Torr in hypoxic and, by 13 Torr, in nonhypoxic animals. There was a concomitant fall in PaO2 (15 Torr). Serum osmolality rose rapidly after rapid infusion of HCO3-. Rapid infusion of hypertonic bicarbonate into an animal or infant whose ventilation is fixed thus results in a less than predicted elevation of arterial pH. PaCO2 rises, PaO2 falls, and serum osmolality rises. The net result may be a worsening rather than an improvement in the animals' metabolic state.

Pulmonary complications, ventilation and blood gases after upper abdominal surgery.

Forty patients who underwent elective cholecystectomy were examined preoperatively and during the first postoperative week by physical examination, measurement of FVC and FEV1, arterial pH and blood gas analyses, and chest x-ray. Postoperative pulmonary complications (p.p.c.) were detected in 30 (75%) of the patients. Simple auscultation was the most sensitive tool in discovering p.p.c., but 18 of the 30 patients with complications also had a pathological chest x-ray. Obesity, smoking postoperative naso-gastric tube and postoperative wound infection were predisposing factors for p.p.c. Six patients with preoperative pulmonary disease all had a progress in their lung pathology. There was no definite relationship of duration of anaesthesia or drainage of the abdominal wound to development of p.p.c. The patients with p.p.c. showed a deeper and more prolonged fall in Pao2 postoperatively than the normal group. None of the normals showed an arterial Po2 below 70 mmHg in the postoperative course, while 63% of the p.p.c. group did. FVC and FEV1 showed marked reductions from preoperative values on the first postoperative day, and then gradually increased to near preoperative values after 1 week. Arterial pH and Pco2 showed no definite changes during the postoperative course.

Arterial blood gas tensions during upper gastrointestinal endoscopy.

Arterial blood gas tensions were measured before and during upper gastrointestinal endoscopy, with (group I) and without (group 2) sedation with intravenous diazepam. There was a highly significant fall in the PaO2, which occurred in both groups and was therefore not attributable to diazepam. Measurement of FEV, and FVC before endoscopy had no predictive value for those patients whose PaO2 fell the most.